The present invention relates generally to methods of separating organic compounds. More specifically, the present invention relates to a method of separating proteins.
In many industries, it is desirable to separate proteins. For example, in research, it is necessary to separate proteins in order to determine whether a given component is providing certain characteristics or results. In other industries, such as pharmaceuticals, food industries, and cosmetics, it is necessary to separate proteins in order to provide certain products or improve products. Furthermore, it may be desirable to separate proteins as a diagnostic tool or treatment. However, there are a variety of other reasons and needs for separating proteins.
There are a variety of methods for separating proteins. Separation can be based on: molecular size; solubility; electric charge; differences in absorption characteristics; and biological affinity for other molecules. Examples of such methods include: ion exchange; gel filtration; hydrophobic chromatography; and specific chromatographies by use of monoclonal antibodies. Ion exchange functions to separate proteins by charge, while gel filtration functions to separate the proteins by weight and shape. Two commonly used materials for ion exchange chromatography are: diethylaminoethylcellulose (DEAE-cellulose); and carboxymethylcellulose (CM-cellulose). DEAE-cellulose contains positively charged groups at pH 7.0 and is therefore an anion exchanger. CM-cellulose contains negatively charged groups at neutral pH and is a cation exchanger.
Although, by utilizing the presently available methods, it is possible to separate and purify many proteins, current methods, even when combined, still are not sufficient to resolve all proteins. In this regard, the properties of some related amino acid residues in proteins cannot be individuated by presently available techniques. For example, the inventor of the present invention does not know of a technique that separates proteins on the basis of differences in arginine and lysine ratios except by chromatography at very high pH values wherein denaturation can be expected. Furthermore, the available techniques are not able to separate certain proteins, in certain applications, so as to yield a sufficiently pure product.
There is therefore a need for further methods of separating proteins.